What happens to the YC applications after rejected?
Is there any change they are sold to 3rd parties?
"your idea is important too, but mainly as evidence that you can have good ideas. Most successful startups change their idea substantially.
We're more likely to fund people we know are smart..."
It's the people that are smart, creative and determined that will do well (IMHO).
As has been said before, if you don't think you can win the race against someone else with the same idea, that's not very promising for you. You need more confidence (but not blindingly so), skill and determination to succeed.
edit - From the app itself:
We don't make any formal promise about secrecy, but we don't plan to let anyone outside Y Combinator see these applications, including other startups we fund.
Sigh